The following description of the background of the invention is provided simply as an aid in understanding the invention and is not admitted to describe or constitute prior art to the invention.
The Philadelphia chromosome (Ph) is a translocation between chromosome 9 and 22 t(9;22) (q34;q11) that is found in more than 90-95% of chronic myeloid leukemia (CML), about 20-25% of adult, and 2-10% of childhood acute lymphoblastic leukemia (ALL). See Rowley J O (1973), Nature 243: 290-293. Catovsk (1979) Br. J. Haematol. 42: 493-498; Prist, et al. (1980) Blood 56: 15-22. In CML, most of the translocation falls in the major breakpoint cluster region (M-bcr) of the bcr gene, and results in two bcr/abl mRNA molecules with a b2a2 or b3a2 junction which encode p210bcr/abl fusion protein. See Konopka, et al., (1984) Cell 37: 1035-1042. In ALL, about two thirds of the bcr breakpoint falls in the minor breakpoint cluster region (m-bcr), and the hybrid bcr/abl transcript contains an e1a2 junction and is translated as a p190bcr/abl fusion protein. See Clark, et al. (1987) Science 235: 85-88. Because CML is a clonal disease, detection of bcr/abl fusion transcripts should precisely reflect CML disease activity. bcr/abl mRNA can be specifically and efficiently detected by the reverse transcription—polymerase chain reaction (RT-PCR), because this fusion gene is leukemia specific and can be used as a marker to identify residual disease after therapy. Quantitative RT-PCR detection of bcr/abl fusion is well established in CML diagnostics, and PCR positivity is virtually diagnostic of this type of leukemia. Kawasaki, et al., (1988) Proc Natl Acad Sci (USA) 85: 5698-5702. Gibson, et al., (1996) Genomic Res 6:995-1001.
However, the present methods of CML or ALL diagnostics are lacking in that for the qualitative assay (that is indication of presence or absence of the disease and not a quantitative number of cells present or other quantitative information provided) uses hazardous radioactive isotopes, complex hybridizations and takes about five days. Further, the present methods do not provide for a single container method of assaying for all three translocation products and providing reproducible and easily and meaningfully interpretable results.
Accordingly, it would be desirable to provide assay methods for bcr/abl translocations that are convenient to carry out, provide highly reproducible qualitative and quantitative results and in which all three translocations may be assayed for at once in one container.